A method for continuous dyeing of woven cotton fabrics has been known for a long time, in which method the fabric passes through a padding machine followed immediately by a steamer and is subsequently washed out.
Such a method cannot be used for cotton knot fabrics because a cut knit fabric is not sufficiently dimensionally stable, and because it is not possible to prevent the edges of the length of fabric from rolling up.
It is preferred to use uncut tubular fabric, but said fabric is encumbered with the drawback that the two edges resulting from the squeezing procedure in the padding machine absorb a great amount of dyestuff and therefore appear as dark stripes. In connection with vat dyeing attempts have been made to solve this problem by ballooning the tubular fabric one or several times during its passage through the steamer in which the fixation occurs, cf. German Offenlegungsschrift No. 3.422.759.
The present invention is based on the same technique, i.e. ballooning the tubular fabric one or several times during its passage through the steamer.
Dyeing with reactive dyes is, however, encumbered with a different problem than dyeing with vat dyes as the latter method requires a feeding of fixation chemicals. These fixation chemicals are very conveniently fed through the liquid locks forming the inlet and the outlet of the steamer. Fabrics dyed with reactive dyes do not require a feeding of fixation chemicals and can pass through the steamer directly from the padding or the swelling phase provided the ballooning technique is not used in the steamer. When the latter technique is used it is necessary that the length of fabric passes a lock such as a trap, in order to maintain the pressure inside the steamer. The latter procedure has, however, a damaging effect on the fabric dyed with reactive dyes because the dye is washed out by water.